A conventionally known machine tool includes a spindle configured to hold and rotate a workpiece, a cutting tool configured to cut the workpiece, feeding means configured to feed the cutting tool toward the workpiece in a predetermined feeding direction by moving the spindle and the cutting tool relative to each other, and vibration means configured to vibrate the spindle and the cutting tool relative to each other. An example of this conventional machine tool is described in United States Patent Publication 2014/0102268, published on Apr. 17, 2014. A control apparatus of the machine tool is configured to control the spindle, the feeding means, and the vibration means to drive the machine tool, and to allow the machine tool to machine the workpiece by the rotation of the spindle and the feed movement of the cutting tool with reciprocating vibration toward the workpiece in the feeding direction.
The conventional machine tool is configured so that an operation instruction is issued by a control apparatus at a predetermined cycle. Therefore, the vibration frequency at which the workpiece holding means and the tool rest vibrate relative to each other is defined as a limited value attributable to a cycle during which the operation instruction can be issued by the control apparatus. However, the above vibration frequency is not considered in the conventional machine tool. Therefore, with respect to any number of rotations of the relative rotation, the reciprocating vibration may not be performed at any number of vibrations of the cutting tool relative to the workpiece during one rotation of the workpiece. Also, in the foregoing conventional machine tool, the vibration frequency or the like by the vibration means is set on the premise that the spindle is rotated; therefore, vibration cutting may not be controlled without rotating the spindle.
Thus, the present invention is intended to solve the above problems of the prior art, that is, it is an object of the present invention to provide a control apparatus of a machine tool and the machine tool, which allows reciprocating vibration in consideration of a vibration frequency, increase flexibility in machining a workpiece, and can perform vibration cutting without rotating a spindle.